Since the oil crisis of the 1970s, we've seen some major technical advances in windows. First came the invention of double-glazing (mass-produced in Switzerland between 1973 and 1995), followed by the insertion of gas between the two (and now three) panes of glass. These technical inventions have made it possible to drastically increase the thermal values of windows, which have fallen from around 6 W/m²K to as little as 0.5 W/m²K in less than 50 years.At the same time, ecological norms and standards have been continually updated to encourage the installation of these increasingly efficient windows in new buildings and facade renovations. For this reason, windows are simply replaced and old one dumped, except in historic buildings, where careful renovation is attempted. At best, the glass of the windows is recycled into other glass products with a lot of effort and at extremely high temperatures, which emit a lot of CO2. Even though in Switzerland we are quite exemplary when it comes to recycling glass, the situation is not so good when it comes to window glass. Only about 20% of window glass is recycled because it requires higher temperatures (1600 degrees instead of 1000) than normal glass and often contains inseparable chemical components.

The aim of the «Windows Of Opportunities» project is to develop a solution for limiting window waste. The aim is to recover windows in good conditions and turn them into a new type of window that meets today's standards. This is accomplished by planing, doubling, and screwing together the sections of the double-glazed window, followed by sealing them with a joint, to create a quadruple-glazed window with a U-value of at least 1.0 W/m²K. This solution not only saves CO2 associated with the extraction of new raw materials and the production of new windows, but also enhances a building's thermal insulation values. Furthermore, it reduces the amount of waste produced. The goal is to introduce a new entity into the window supply chain responsible for quality control of re-used windows, enabling the provision of guarantees, and facilitating integration within existing networks.